content: /* Copyright (C) 2016-2018 Alibaba Group Holding Limited
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import java.io.IOException;
  import java.util.AbstractMap;
  import java.util.Map;
  
  /**
   * Implements the lite version of map entry messages.
   *
   * This class serves as an utility class to help do serialization/parsing of
   * map entries. It's used in generated code and also in the full version
   * MapEntry message.
   *
   * Protobuf internal. Users shouldn't use.
   */
  public class MapEntryLite<K, V> {
  
    static class Metadata<K, V> {
      public final WireFormat.FieldType keyType;
      public final K defaultKey;
      public final WireFormat.FieldType valueType;
      public final V defaultValue;
  
      public Metadata(
          WireFormat.FieldType keyType, K defaultKey,
          WireFormat.FieldType valueType, V defaultValue) {
        this.keyType = keyType;
        this.defaultKey = defaultKey;
        this.valueType = valueType;
        this.defaultValue = defaultValue;
      }
    }
  
    private static final int KEY_FIELD_NUMBER = 1;
    private static final int VALUE_FIELD_NUMBER = 2;
  
    private final Metadata<K, V> metadata;
    private final K key;
    private final V value;
  
    /** Creates a default MapEntryLite message instance. */
    private MapEntryLite(
        WireFormat.FieldType keyType, K defaultKey,
        WireFormat.FieldType valueType, V defaultValue) {
      this.metadata = new Metadata<K, V>(keyType, defaultKey, valueType, defaultValue);
      this.key = defaultKey;
      this.value = defaultValue;
    }
  
    /** Creates a new MapEntryLite message. */
    private MapEntryLite(Metadata<K, V> metadata, K key, V value) {
      this.metadata = metadata;
      this.key = key;
      this.value = value;
    }
  
    public K getKey() {
      return key;
    }
  
    public V getValue() {
      return value;
    }
  
    /**
     * Creates a default MapEntryLite message instance.
     *
     * This method is used by generated code to create the default instance for
     * a map entry message. The created default instance should be used to create
     * new map entry messages of the same type. For each map entry message, only
     * one default instance should be created.
     */
    public static <K, V> MapEntryLite<K, V> newDefaultInstance(
        WireFormat.FieldType keyType, K defaultKey,
        WireFormat.FieldType valueType, V defaultValue) {
      return new MapEntryLite<K, V>(
          keyType, defaultKey, valueType, defaultValue);
    }
  
    static <K, V> void writeTo(CodedOutputStream output, Metadata<K, V> metadata, K key, V value)
        throws IOException {
      FieldSet.writeElement(output, metadata.keyType, KEY_FIELD_NUMBER, key);
      FieldSet.writeElement(output, metadata.valueType, VALUE_FIELD_NUMBER, value);
    }
  
    static <K, V> int computeSerializedSize(Metadata<K, V> metadata, K key, V value) {
      return FieldSet.computeElementSize(metadata.keyType, KEY_FIELD_NUMBER, key)
          + FieldSet.computeElementSize(metadata.valueType, VALUE_FIELD_NUMBER, value);
    }
  
    @SuppressWarnings("unchecked")
    static <T> T parseField(
        CodedInputStream input, ExtensionRegistryLite extensionRegistry,
        WireFormat.FieldType type, T value) throws IOException {
      switch (type) {
        case MESSAGE:
          MessageLite.Builder subBuilder = ((MessageLite) value).toBuilder();
          input.readMessage(subBuilder, extensionRegistry);
          return (T) subBuilder.buildPartial();
        case ENUM:
          return (T) (java.lang.Integer) input.readEnum();
        case GROUP:
          throw new RuntimeException("Groups are not allowed in maps.");
        default:
          return (T) FieldSet.readPrimitiveField(input, type, true);
      }
    }
  
    /**
     * Serializes the provided key and value as though they were wrapped by a {@link MapEntryLite}
     * to the output stream. This helper method avoids allocation of a {@link MapEntryLite}
     * built with a key and value and is called from generated code directly.
     */
    public void serializeTo(CodedOutputStream output, int fieldNumber, K key, V value)
        throws IOException {
      output.writeTag(fieldNumber, WireFormat.WIRETYPE_LENGTH_DELIMITED);
      output.writeUInt32NoTag(computeSerializedSize(metadata, key, value));
      writeTo(output, metadata, key, value);
    }
  
    /**
     * Computes the message size for the provided key and value as though they were wrapped
     * by a {@link MapEntryLite}. This helper method avoids allocation of a {@link MapEntryLite}
     * built with a key and value and is called from generated code directly.
     */
    public int computeMessageSize(int fieldNumber, K key, V value) {
      return CodedOutputStream.computeTagSize(fieldNumber)
          + CodedOutputStream.computeLengthDelimitedFieldSize(
              computeSerializedSize(metadata, key, value));
    }
  
    /**
     * Parses an entry off of the input as a {@link Map.Entry}. This helper requires an allocation
     * so using {@link #parseInto} is preferred if possible.
     */
    public Map.Entry<K, V> parseEntry(ByteString bytes, ExtensionRegistryLite extensionRegistry)
        throws IOException {
      return parseEntry(bytes.newCodedInput(), metadata, extensionRegistry);
    }
  
    static <K, V> Map.Entry<K, V> parseEntry(
        CodedInputStream input, Metadata<K, V> metadata, ExtensionRegistryLite extensionRegistry)
            throws IOException{
      K key = metadata.defaultKey;
      V value = metadata.defaultValue;
      while (true) {
        int tag = input.readTag();
        if (tag == 0) {
          break;
        }
        if (tag == WireFormat.makeTag(KEY_FIELD_NUMBER, metadata.keyType.getWireType())) {
          key = parseField(input, extensionRegistry, metadata.keyType, key);
        } else if (tag == WireFormat.makeTag(VALUE_FIELD_NUMBER, metadata.valueType.getWireType())) {
          value = parseField(input, extensionRegistry, metadata.valueType, value);
        } else {
          if (!input.skipField(tag)) {
            break;
          }
        }
      }
      return new AbstractMap.SimpleImmutableEntry<K, V>(key, value);
    }
  
    /**
     * Parses an entry off of the input into the map. This helper avoids allocaton of a
     * {@link MapEntryLite} by parsing directly into the provided {@link MapFieldLite}.
     */
    public void parseInto(
        MapFieldLite<K, V> map, CodedInputStream input, ExtensionRegistryLite extensionRegistry)
            throws IOException {
      int length = input.readRawVarint32();
      final int oldLimit = input.pushLimit(length);
      K key = metadata.defaultKey;
      V value = metadata.defaultValue;
  
      while (true) {
        int tag = input.readTag();
        if (tag == 0) {
          break;
        }
        if (tag == WireFormat.makeTag(KEY_FIELD_NUMBER, metadata.keyType.getWireType())) {
          key = parseField(input, extensionRegistry, metadata.keyType, key);
        } else if (tag == WireFormat.makeTag(VALUE_FIELD_NUMBER, metadata.valueType.getWireType())) {
          value = parseField(input, extensionRegistry, metadata.valueType, value);
        } else {
          if (!input.skipField(tag)) {
            break;
          }
        }
      }
  
      input.checkLastTagWas(0);
      input.popLimit(oldLimit);
      map.put(key, value);
    }
  
    /** For experimental runtime internal use only. */
    Metadata<K, V> getMetadata() {
      return metadata;
    }
  }
  